Chapter 3: Sensation, Perception and Human Potential
Chapter 3: Sensation, Perception and Human Potential
Hearing and other Senses
Hearing
The exhilarating ripple of her voice was a wild tonic in the rain.
Scott Fitzgerald, The Great Gatsby
Humans rely heavily on hearing as well as vision to survive and enjoy our surroundings. Sound can help us detect the presence of and locate objects which are at great distances or out of sight. Speech communication relies on the ability to hear. If you are similar to most college students, you spend a considerable amount of time listening to music. As expressed by Fitzgerald, the voice of a loved one can soothe and exhilarate us.
Our ears detect and process the vibrations produced by sound waves. When graphed, the amplitude (loudness) of a sound is indicated by the height from top to bottom of a wave cycle. The pitch (low bass vs. high treble) is a function of the frequency of waves per unit of time (see Figure 3.11).
Figure 3.11 Amplitude and frequency of sound waves.
Video
Watch the following video for a description of how wavelength, frequency, and amplitude affect hearing:
Loudness is measured in decibels. Figure 3.12 shows the decibel levels of some common events. Please be careful about exposing yourself to loud sounds. It is possible to permanently damage your hearing by prolonged exposure to loud music, whether at concerts or when listening with headphones.
Figure 3.12 Decibel Levels of Common Events.
Figure 3.13 shows the major parts of the ear involved in the transduction process converting sound waves into electronic signals transmitted to the brain, primarily the temporal lobe of the cerebral cortex.
Figure 3.13 Anatomy of ear (brown is outer ear, red is middle ear, purple is inner ear).
The ear can be divided into the outer ear , middle ear , and inner ear . The outer ear includes the ear flap, ear canal, and eardrum. The middle ear is in an enclosed chamber behind the eardrum and includes the three tiniest bones (ossicles) in the body often described as the hammer, anvil, and stirrup. The inner ear consists of the cochlea, a snail shaped tube filled with fluid. When sound waves reach the eardrum they cause it to vibrate. These vibrations are amplified by the ossicles and transmitted to the cochlea. The limits of human hearing are determined by the nature of tiny hair cells contained within the basilar membrane lining the cochlea (see Figure 3.14). Starting at the end (apex) of the cochlea, the hair cells are responsive to increasing frequencies of sound waves. Human hearing extends approximately from 20 to 20,000 Hz (vibration cycles per second). The neural information from the basilar membrane is transmitted to the auditory nerve and then to the brainstem.
Figure 3.14 The cochlea.
Smell and Taste
One of the very nicest things about life is the way we must regularly stop whatever it is we are doing and devote our attention to eating.
Luciano Pavarotti and William Wright, from Pavarotti, My Own Story
Figure 3.15 portrays the different cells for salt